Chevy LT1 Engine Build - Power Play

The Second-Gen LT1 Is A Great Engine--Our Plan Is To Make It Better!

Manley 6-inch forged H-beam connecting rods proved to be the perfect choice for our combination. Not only are they strong, but they are light as well. Nicely machined SRP pistons round out the reciprocating assembly. With a short-skirt design, they will help keep the weight to a minimum. Rounding out our bulletproof short-block are items like the Cloyes heavy-duty single-roller timing chain and gears, a complete valvetrain assembly from Crane Cams, performance gaskets from Fel-Pro, and top-of-the-line fasteners from ARP.

First consideration was the engine block itself. In order to maintain the LT1 heritage (and logistically install it in a fourth-generation Camaro), it was necessary to use a late-model case designed to accept the front-mounted distributor and accommodate the reverse cooling water flow and its accompanying direct-drive waterpump. But, since we were gunning for lots of torque, we had to strengthen the less-than-stout main bearing saddles. The first step was to contact the folks at Pro Gram Engineering for a set of their billet splayed four-bolt caps. These well-machined parts go a long way in beefing up the lower end. As for a crankshaft, there are plenty of cast-iron units out there. And, since we were determined to add a significant number of cubes, we knew we'd have to contact one of the industry's custom crank makers to find a strong forged arm. Here, we turned to Cola Crankshaft Company. They provided a 4-inch stroke, non-twist 4340 forging that is, to say the least, a work of art. Not only does it accept the smaller-diameter flywheel and one-piece rear seal that identify a late-model version, but it is also drilled to allow use of a bolt for holding the harmonic balancer in place.

As for the rest of the reciprocating assembly, a lot of thought went into what connecting rods were needed and what pistons to use. On both fronts, we didn't skimp, opting for a set of Manley forged H-beam units and SRP forged slugs. And since we were planning on adding a good dose of compression from the supercharger, we had the pistons created so that the final compression ratio was in the neighborhood of 9.4:1, a full one point less than the factory hypereutectic versions.

With the short-block laid out as tough as possible, attention was given to the engine's breathing capacity. The biggest decision was in what heads to use. With an industry ripe with stellar designs, it wasn't an easy choice. But when all the information was assessed, we chose to go with Air Flow Research's LT1 design, which is a direct replacement for the factory units. That's where the similarity ends, though, as these CNC'd beauties feature 2.08-inch intake valves and 1.60-inch exhausts. And, once Beck was finished massaging them, they showed an impressive 280-cfm intake (at .500-.600-inch of valve lift) on the flow bench! Impressive, to say the least.

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Topping off our potent late-model mouse, and completing the first part of our Beck Racing Engines buildup, is a set of Airflow Research LT1 aluminum cylinder heads. These awesome reverse-flow castings feature oversize Manley Severe Duty 2.08-inch intake and 1.60-inch exhaust valves, 76cc chambers, and large CNC'd ports. With the addition of the Crane Cams matching valve springs and chrome-moly retainers, these heads complete the 383's long-block. Additional grinding by the head gurus at Beck Racing Engines enlarged the ports and yielded an awesome 280-cfm port volume on the intake side. The exhausts, which are perhaps the more important of the two on a supercharged engine, flowed equally well and maintained the important "D" shape.

While the cylinder heads give our late-model bruiser a set of large-capacity lungs, there's no question that its heart (and degree of power) will be determined by whatever camshaft is installed. Here, we turned to the trusted gurus at Crane Cams, who came up with a custom grind that is designed to make a ton of power and torque with a supercharger and still be civil when it comes to idling at a stop light. The hydraulic roller grind we were given has more lift and duration on the exhaust side (.352-inch at the lobe and 292 degrees of advertised duration) to help quickly scavenge the burned gasses from the forced induction. This is equally, if not more, important on a supercharged powerplant, and especially so in a street-driven environment. On the intake side, however, there is sufficient lift and duration to gulp all that the ProCharger can force feed it. Lift at the cam is a not-to-short .339-inch, while advertised duration comes in at 284 degrees. What do those lift numbers equal after they're multiplied by the Crane 1.6:1 roller rocker arms? How's .542 inch at the intake valve and .563 inch at the exhaust hit you?

Coupling the cam and crank together is the job of the Cloyes true-roller timing chain and billet gears. With a modern LT1, there isn't room for a double-roller setup or a belt drive (remember, the Opti-spark ignition resides just ahead of the chain assembly and the waterpump drive connects to a straight-cut gear on the backside of the cam sprocket), therefore we were limited to the OEM design. Not to worry, though, we've heard of some pretty powerful engines doing well on a single-roller chain, so we were confident that the Cloyes setup would take all we were going to throw at it.

The balance of the valvetrain includes the aforementioned Crane roller rockers and lifters (which, unlike the individual factory design, use a tie bar to pair them together), Crane chrome-moly pushrods and matching valve springs and retainers. All told, the components will allow our big-inch mouse to spin freely to 6,500 rpm. Keeping all of our Clevite bearings and internal parts lubricated is the responsibility of the Titan Sportsman oil pump residing in a Billet Fabrication extra-capacity aluminum oil pan. This duo has proven itself time and again, and we're sure that the oil will do its job.

While this part of our buildup (we'll offer up Part 2 next month) was intended to concentrate on the long-block machining, blueprinting and assembly, it's important to let you know that in addition to the ATI D-1 Procharger, the balance of the induction system will be as close to the original-design tuned port injection as possible. In fact, the intake itself is a factory version, with the important exception that it has been totally reworked by the experts at Arizona Speed and Marine (and further smoothed by Extrude Hone). Coupled with an Arizona Speed and Marine 58mm billet throttle body, we're confident that our 383 will have no breathing problems whatsoever. So, until next month, when we discuss how all of the external parts come together and then venture off to the Vrbancic Brother's dyno to see what she makes, follow along as we visit Beck Racing Engines for some precision machine work and assembly.

Our Beck Racing Engines-built LT1 383 uses a combination of parts designed for durability and precision from a virtual who's who of the aftermarket.

For starters, the stock block gets its share of upgrades with a set of billet four-bolt main caps from Pro Gram Engineering. To make the extra 33 cubes from the basic 350 case, a combination of .030-inch overbored cylinders and a beautiful 3.75-inch 4340 forged-steel Cola crankshaft is used.

Manley 6-inch forged H-beam connecting rods proved to be the perfect choice for our combination. Not only are they strong, but they are light as well. Nicely machined SRP pistons round out the reciprocating assembly. With a short-skirt design, they will help keep the weight to a minimum. Rounding out our bulletproof short-block are items like the Cloyes heavy-duty single-roller timing chain and gears, a complete valvetrain assembly from Crane Cams, performance gaskets from Fel-Pro, and top-of-the-line fasteners from ARP.

Topping off our potent late-model mouse, and completing the first part of our Beck Racing Engines buildup, is a set of Airflow Research LT1 aluminum cylinder heads. These awesome reverse-flow castings feature oversize Manley Severe Duty 2.08-inch intake and 1.60-inch exhaust valves, 76cc chambers, and large CNC'd ports. With the addition of the Crane Cams matching valve springs and chrome-moly retainers, these heads complete the 383's long-block. Additional grinding by the head gurus at Beck Racing Engines enlarged the ports and yielded an awesome 280-cfm port volume on the intake side. The exhausts, which are perhaps the more important of the two on a supercharged engine, flowed equally well and maintained the important "D" shape.

The first step to our engine build was to secure a good, seasoned late-model LT1 block and get to work massaging it. Here, the performance gurus at Beck Racing Engines took a die grinder and smoothed out all of the sharp and rough areas. This process, although aiding in the aesthetics of the engine, is mainly intended to help prevent cracks from starting.

Once the hole was created, a tap was used to create the threads.

Here, the main bearing saddles, with the three new Pro Gram billet four-bolt caps, is being align-bored. Once the fit is close, all five caps are align-honed to final size.

One of the most important machining process undertaken at Beck's was to convert the original two-bolt main bearing saddles to the much stronger four-bolt design. The conversion process begins by relieving the block where the main bearing cap sits. A step-down was machined using this large end mill. Alignment is critical at this step, or the Pro Gram billet cap won't sit flat and distribute its load accordingly.

With three new main bearing caps installed the next step is to align-bore the main saddle to ensure the crank rotates in round holes. Here, the stock front cap is checked to see how much material needed to be removed from the flat mounting surface. This process was repeated for all of the new Pro Gram caps, as well.

Note how the edge of the main saddle is beveled. This is a nice touch to making sure the block is blueprinted and that there are no places for cracks to begin.

The Pro Gram billet caps use a splayed outer bolt location. With the block machined to accept the cap, it was bolted in place with the existing two bolts and set in the mill. Then the correct angle was set and the holes were drilled using this special bit.

A factory rear cap is used, and prior to having the saddles align-fit a base from an old oil pump is torqued down to simulate the load placed on the bearing cap once the oil pump is installed.

Here's a comparison of an unmodified rear cap and one that Beck massages for better oiling. Note the enlarged cavity adjacent to the bolt hole and inlet port. A die grinder is used to smooth out and blend this area.

Prior to final honing, the tops of each bore are chamfered by hand using this large sanding cone in an electric drill. This procedure not only provides an easy entrance for the hone stones, but when it comes time for the piston rings to go in, it offers a smoother transition than if a sharp edge been left.

Moving on to other parts of our short-block, the beautiful Manley H-beam rods got a once over before heading off to the balancer.

Both ends were checked for roundness and size and were found to be right on target.

Once the lower end is machined and the oil pan rails have been checked for flatness, the block is then squared and the deck heights are matched. The measurement is taken from the crank centerline, where it should be 9 inches. In our block's case, .025-inch was machined off to get the number right.

The importance of using a torque plate during final cylinder honing may not be that widely understood by the average home engine builder. But since torquing a head in place does distort the surrounding material, it makes sense to simulate that while finishing the cylinder wall surface. That way, it's sure to be as close to being round as possible.

SRP's forged piston is a piece of art. Prior to boring the block, the skirts were miked to determine what the piston-to-cylinder-wall clearance would be. Needless to say, they were perfect right out of the box. As is standard practice for Beck Racing Engines, the pin bores received a slight hone to zero in on the clearance that Beck likes to see.

When it comes to gaining cubic inches, enlarging the bore is the first place most engine builders go. While cutting a nominal .030-inch out of a stock 350's cylinder wall will only add approximately 5 inches to the displacement, it does provide a new surface for the rings to seat. Beck cut .024-inch with the boring bar and then finish-honed the cylinders to size.

The final process the LT1 block received was to have the cam bearing saddle honed. This leaves a good surface for the bearings to fit in. Once the block was finished being machined it was off for another round in the cleaning tank.

There are few things--if any--more important when assembling a precision engine than cleanliness.

Prior to the short-block being assembled, Beck installed a small oil plug above the rear main bearing cap. Without this plug in place, the engine would have an internal oil leak and lack oil pressure.

The Manley rods were close to weighing the same right out of the box, however, Beck took that one further step and made sure each one was exactly the same.

Through a battery of tests, the crank is rotated and it is determined, based on rotational degrees, where material must be removed or added in order to get the assembly to zero balance.

With the block machining complete, and the rods and pistons checked for proper specs, it was off to the other room to have the reciprocating assembly balanced. Every powerplant that Beck Racing Engines builds has a complete worksheet filled out with all of the information, from machining processes to balance specs. Here a rod bearing is weighed and the numbers are logged onto the sheet.

Fortunately, the Cola crank needed to have material removed rather than added on. A large drill did the job in this location, simply removing material from within the counterweight.

In another location, a grinder was used to remove material from the outside of a center counterweight.

When all was said and done, the crank registered about as close to zero balance as you can get: negative .03 grams at each end.

Once off the balancer, the crank's journals were given a quick polish and set aside to await installation.

As mentioned earlier, the AFR aluminum heads are precision castings. Once the port work and cc'ing of the combustion chambers and valve grinding was complete, Beck had his cylinder specialist spend some time with them on the flowbench. While this data is important when calculating how well an engine breathes, it's worth becomes really apparent when the correct combination of valvetrain components is used and the engine makes the desired power and torque. All we can say at this stage is that these heads did their job perfectly.

The massaging of all three elements of the AFR heads is obvious here. Note the "D" shape of the exhaust port...

...the contour of the large intake runners...

...the unshrouding of the valves in the combustion chamber, and the clean look of the bowls.

No Plastigauge here. Bearing clearances were determined using a micrometer for the crank and a dial-bore gauge for the main bearing saddles with the bearings torqued in place, of course. By subtracting the diameter of the journal from the inside diameter of the bearings a true running clearance was ascertained.

With ARP main bearing studs in place, and the crank cleaned of all metal shavings and debris...

...it was meticulously put in the main bearing saddle and the Pro Gram caps were given the correct torque load. The result: our Cola crank spun effortlessly.

From there it was on to readying the rod and piston assembly for installation. First step was to arrive at all of the correct end gaps for the C&A moly rings. This handy grinder made the job a lot easier than doing it by hand.

Note how the ends of the ring come together, thus providing a "gapless" fit.

This view is of the final piston/rod assembly prior to having the rings installed. Note the stout Manley H-beam rod with ARP bolts securing the cap instead of more commonly used studs. Also apparent is how short the skirts are and the wrist pin placement of the SRP forged piston.

Because we used a 6-inch connecting rod, the pin location in the piston is up high, actually cutting through the oil ring land. No problem, as the assembly includes a pair of solid rings that act as a seat for the gap created by the wrist pin.

A prerequisite for a performance engine is the use of full-floating wrist pins rather than those that are pressed into the rod's small end. The pins are secured in the pistons with these retainers, known as Spiralocks. The retainer is literally uncoiled and fits in a groove cut in the piston's wrist pin bore. Installing them is relatively easy. Having to take them out can be a pain in the you-know-what!

With all of the piston/rod assemblies installed in the block, the next step was to check clearances, or do what is commonly referred to as blueprinting. Here the rod's side clearance is checked with a feeler gauge.

Since the LT1 350 wasn't designed for a stroker crank assembly, the block had to be notched in certain places where the rod bolt could come in contact with it. Another modification required machining the head of a couple select rod bolts so they maintained the proper clearance on their journey.

The heart of this stout LT1 383 is its Crane hydraulic roller bumpstick. Making sure all the surfaces get some assembly lube will go a long way toward a successful break-in period. Though this was a custom grind for our project, the specs aren't top secret, with .339-inch intake lift and .352-inch on the exhaust (at the cam), and a healthy advertised duration of 284-degrees intake and 292-degrees exhaust, this will definitely help our heads to inhale and exhale the supercharged mix from the ATI Procharger.

Here's one of those quirky differences between a basic small-block and the second-generation LT1. This is the gear assembly for the front-driven waterpump, unique to the LT1. It resides just above the cam and engages with a straight-cut gear incorporated into the back of the camshaft sprocket. Making sure the bearing is in good shape and lubed for initial break-in is a plus. We'd hate to have this motor fail due to some part like this odd piece breaking.

Another place the LT1 differs with its earlier brethren is how a retention plate is used to keep the cam from walking in the block. For years, small-blocks using a roller cam were required to use a cam "button" on the end that limited forward movement. Since the factory installed roller cams as standard equipment, this device was incorporated to do the same job.

Here's how the crankshaft's endplay is measured. There should be no more than .005-.007-inch movement here.

Since the engine's distributorless ignition, known as the Opti-spark, drives off of the front of the engine, the camshaft dowel pin, primarily used to align the cam's sprocket, is different, as well. For late '95 through '97 models, the Opti-spark uses this longer dowel to align itself with the cam/crank assembly. Earlier second-generation LT1s used a splined shaft that sometimes made correct alignment a trial-and-error procedure.

Here's the relationship of the stout Cloyes true roller timing chain and billet cam sprocket with the waterpump drive. Note the splined gear on the back.

With all of the internal components safely torqued in place, Beck installed a degree wheel to check to see that all of the cam's specs are where they're supposed to be. Dead-on was what the wheel showed.

This dial indicator was set up to verify camshaft lift at the lobe. Again, the Crane cam measured up to its specifications card.

The last step before leaving BRE's Phoenix-based operation was to install the AFR cylinder heads. This essentially completed our stay there, and although the heads were bolted on at Beck's using ARP fasteners, since we knew that we were going to pump in a few pounds of boost with the ATI Procharger, we opted to swap out the bolts for a set of ARP studs.

In this Tech article, we test to see what kind of magic can be done on a 408 stroker by using a Crane cam to do a cam swap. The results definitely do not lie that this swap will give you an exponential increase in both torque and horsepower. » Read More